Control method for inhibiting harmonic distortion of input current

Abstract

A control method is used in a power factor corrector. Firstly, a current command signal from a computing circuit is received. Then, the current command signal is compared with an input signal of the power conversion circuit, so that a current error signal is generated. If the power factor corrector is operated in a transition interval between the first mode and the second mode, an addition operation is performed on the unadjusted current error signal, a feedforward signal and the adjusted current error signal, thereby generating a current control signal. A switch control signal is generated according to the current control signal. A switching element of a power conversion circuit is controlled according to the switch control signal. Consequently, the harmonic distortion of the input current is inhibited.

What is claimed is: 
     
       1. A control method of inhibiting harmonic distortion of an input current for use in a power factor corrector, the power factor corrector being connected with a power conversion circuit and comprising a computing circuit, the power factor corrector being operated in a first mode or a second mode, the control method comprising at least steps of:
 (a) receiving a current command signal from the computing circuit; 
 (b) comparing the current command signal with an input signal of the power conversion circuit, thereby generating a current error signal; 
 (c) adjusting the current error signal; 
 (d) judging whether the power factor corrector is operated in a transition interval between the first mode and the second mode, wherein if the judging condition is satisfied, an addition operation is performed on the unadjusted current error signal, a feedforward signal and the adjusted current error signal, thereby generating a current control signal; and 
 (e) generating a switch control signal according to the current control signal, and controlling a switching element of the power conversion circuit according to the switch control signal, thereby inhibiting harmonic distortion of the input current. 
 
     
     
       2. The control method according to  claim 1 , wherein the power factor corrector is electrically connected with a switch control circuit, wherein the switch control circuit generates the switch control signal according to the current control signal and a reference signal. 
     
     
       3. The control method according to  claim 1 , wherein the step (c) of adjusting the current error signal is performed by amplifying the current error signal. 
     
     
       4. The control method according to  claim 1 , wherein the first mode is a discontinuous conduction mode, and the second mode is a continuous conduction mode. 
     
     
       5. The control method according to  claim 4 , wherein the minimum duty cycle between a duty cycle of the first mode and a duty cycle of the second mode is defined as the feedforward signal. 
     
     
       6. The control method according to  claim 1 , wherein the step (a) comprises a sub-step (a1) of receiving a reference voltage and an output voltage from the power conversion circuit and comparing the reference voltage with the output voltage, thereby generating a voltage error signal. 
     
     
       7. The control method according to  claim 6 , wherein the step (a) further comprises a sub-step (a2) of adjusting the voltage error signal. 
     
     
       8. The control method according to  claim 7 , wherein the step (a) further comprises a sub-step (a3) of allowing the computing circuit to perform a multiplication on the voltage command signal, a sinusoidal signal and an inversion signal of the input voltage, thereby generating the current command signal. 
     
     
       9. The control method according to  claim 7 , wherein the sub-step (a2) of adjusting the voltage error signal is performed by amplifying the voltage error signal. 
     
     
       10. The control method according to  claim 1 , wherein if the judging condition in the step (b) is not satisfied, an addition operation is performed on the feedforward signal and the adjusted current error signal, thereby generating the current control signal.